Archived posting to the Leica Users Group, 2001/06/12
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Greg- If you are using the color head to print variable contrast paper, allow me to make a suggestion. I'll preface my remarks by saying that having had a step-tablet, the same one for twenty five years or so, really is not that major an expense, even if you buy the outrageously priced Kodak version, and I have seen them offered on the internet for as little as about $20 for a 21 step tablet. I also made the investment in a used Beseler Color Analyser, some which I have bought for as little as $50 dollars, and then sold to friends who I taught split printing to (at cost, by the way!!) If you use Ilford paper, they have a 'guide' where the approximate steps of contrast are shown with the approximate settings of the color head. As you note, I said 'approximate' since the color heads' calibration is anything but exact, and you would need a densitometer- or enlarging meter! to determaine with any accuracy the true density of any filter setting. What I did was to use each of the settings given, and exposed a strip of paper with a step tablet on top using each 'grade' of filtration, developing, then seeing what the actual contrast grade turned out to be. Since a step tablet like the one I use is divided into 21 steps of density, eachone about .15 absolute optical density more dense than the previous, it gives a fairly wide range of possibilities. IF you think of it as a negative developed to a contrast index of .5 then each step represents one stop of difference in theoretical illumnation of a scene- and could be considered a 'perfect' negative since it captures all the possible tones you might encounter in a one strip. So if you find that there are seven bars of gray on your test strip, then you know that the absolute range of that particular filter setting is seven times .15, or .75. This translates into a density range of .75- from the darkest printable shadow to the lightest detectable highlight! Simply adjusting the filtration either more yellow or more magenta will alter the overall 'grade' and you can very easily adjust the filtration to give you the exact 'grade you want. You can plot several settings on a chart and extraploate to find the exact contrast grade you want. Cyan is very little used, but if you want to use it, it makes little difference- Cyan and Yellow makes a green light, typically you think of it as about 562nm wavelength, and the Cyan and Magenta make Blue- the exact wavelength escapes me, but I think about 450nm. The low contrast emulsion is senitive to the green, and the high contrast emulsion is sensitive to the blue. Varying the two will make the VC paper respond in almost an infinite number of possible grades within the range of its sensitivity. Usually, I can count on Ilford Multigrade to give me a range of three steps at the highest contrast setting to about eleven with the lowest- that means that a negative with a density range it from .45 to 1.65 is printable, though that is 'pushing the envelope, and I rarely have negatives that extreme unless I am doing either very low light work, or sometimes what is called 'high key' portraiture (little girls in white dresses, sitting in a white rattan chair with a white backgound, holding a white teddy bear or kitten!!). Once you have 'calibrated' you can then get very controlling as to what, and how you print. Once you sttle on a good paper/developer combination, you will be an unbeatable printer, and find that you waste a lot less time and material getting what you want!! Just my .02 worth! Good luck, and best of multicolored light to you! Dan